Container seaming machines have been in use in the industry for many years. Referring to FIGS. 1 and 2, a typical container closure operation consists of an infeed conveyor 20 that feeds a constant supply of evenly-spaced, open containers 22 (e.g., metal cans) to a seaming machine 24. Just prior to reaching the seaming machine 24, a cover feed assembly 26 places an end closure 28 over the container opening at a position referred to herein as the “make-up point” 30. The cover feed assembly 26 includes a rotating cover feed turret 32 that moves the end closures 28 along a predefined path. As shown in FIG. 15, the cover feed assembly 26 is formed from a number of separate parts including dual guide sections 34, 38 mounted on the underside of a machine plate 36 and secured with several small bolts (not shown). The end closures 28 are fed from a cover magazine 46 at a predefined rate.
The container 22 has a small outwardly extending flange 48 about its upper opening. The end closure 28 has a similar flange 50, called “curl”. See FIGS. 17 and 15. After the container 22 receives an end closure 28, the combination enters the seaming machine 24 where one or more shaft assemblies 52 (see FIG. 2) fold the flanges 48 and 50 to form an air tight seam. Referring back to FIG. 1, a discharge turret 54 moves the sealed containers along a discharge conveyor 56 for further processing.
In more detail and referring to FIG. 2, the seaming machine 24 includes a lifter table 60 and a seaming head 62 connected to the table 60 via various supports (not shown). Both the lifter table 60 and seaming head 62 are rotatably connected to a central spindle 64 and are arranged to so rotate in unison at a predefined rate. An upper seaming cam 66 is provided above the seaming head 62, though, the cam 66 does not rotate (or at least not at the same speed as the head 62 and table 60). The lifter table 60 has multiple stations 68 that each support an individual container 22. In some embodiments, these stations include “lifters” 70 that physically lift the container 22 upward during the seaming process.
The seaming head 62 includes multiple shaft assemblies 52 outwardly spaced about the seaming cam 66. In FIG. 2, a single shaft assembly is shown for clarity of illustration only. In known machines, there may be anywhere from 1 to 18 shaft assemblies 52 spaced about the head 62. The shaft assemblies 52 provide the components necessary to form a folded seam between a container 22 and its corresponding lid 28. In one embodiment, the shaft assemblies each include an upright shaft 70 that transmits a rotary motion to a pair of rollers 72, 74 via a support block 76. The head assembly also includes multiple chucks 80, one at each container station 68.
Still referring to FIG. 2, during the closure process, an unjoined container 22 and end closure 28 are placed at a station 68 where they are held between a lifter 70 and a chuck 80. Because conventional lids 28 include concentric rings that surround slightly sunken circular areas, the chuck contacts the upper surface of the lid, supporting the chuck wall portion of the lid and providing as such an anvil to perform the seaming operation.
As stated above, the seaming head and lifter table are rotating about the centerline of the spindle 64 during the seaming process. This allows a constant flow of containers through the seaming machine without having to stop the assembly to load and unload the open and sealed containers, respectively. In addition, each container 22 is rotating about its own central axis as well. To close the joint, the rollers 72, 74 of the shaft assembly press the combined flanges 48, 50 against the chuck 80, causing them to deform into a desired shape. The rollers 72, 74 have profiled grooves at their outer circumference that bend the flanges in a specific manner, thus ensuring a perfect seam.
Referring to FIG. 3, prior art shaft assembly 52 includes an upright shaft 70 that is located between adjacent container stations. First and second rollers, 72 and 74, respectively, are connected to the shaft 70 via block 76. The first roller 72 is sized and shaped to effectuate an initial partial curling of a downstream container 82. The second roller 74 is sized and shaped to effectuate a final curling of an upstream container 84. Thus, the shaft assembly operates on two separate containers. The rollers 72 and 74 act on the containers from the stations located to each side of the shaft. Stated differently, a single container is sealed using two separate shaft assemblies. In another embodiment of a shaft assembly (not shown), a single shaft is used with a single roller, with two such shaft assemblies being provided for each station.
The rollers 72 and 74 accomplish their tasks by being pressed against the flanges while the container 22 is rotated about its longitudinally central axis. The position of the block 76 determines which roller will be engaged with a container. The block 76 is connected to the lower end of the shaft 70. Rotary motion is transmitted to the block 76 via first and second cam followers 86 and 88 that are located at the upper end of the shaft 70. See FIG. 2. The cam followers 86 and 88 follow the contours of the seaming cam 66 as the seaming head 62 and lifter table 60 rotate relative to the seaming cam 66. The first cam follower 86 controls the position of the first roller 72. The second cam follower 88 controls the position of the second roller 74.
The above arrangements, while adequate, have a number of disadvantages. The manufacturer must provide machines that are capable of having varying numbers of stations. Each change in the number of stations will require a separate, redesigned shaft assembly to adjust the roller arm length and roller pitch. Similarly, it is difficult and time-consuming for the customer to change the machine setup in this regard. In addition, the cover feed assembly is difficult to install. When changing from one end closure size to another, the entire assembly must be reconfigured and the three part cover guides precisely reset. This is time consuming and often requires special skills, tools, and knowledge.